As covering materials of insulated wires, resin compositions prepared by blending polyvinyl chloride (PVC) with a halogen-derived flame retardant are well known.
However, when these are disposed without being subjected to an appropriate treatment, a plasticizer and/or a heavy metal stabilizer blended in the covering material may be eluted, or when these are combusted, corrosive gases and dioxins may be generated from halogen compounds included in the covering material. Thus, these problems have become a subject of discussion in recent years.
Under such circumstances, investigations of techniques for covering electric wires with a nonhalogen flame-retarding material not accompanied by possibilities of elution of deleterious heavy metals or generation of halogen based gases and the like have been initiated.
Nonhalogen flame-retarding materials attain flame retardance by blending a flame retardant not containing halogen in a resin. As the flame retardant, for example, a metal hydrate such as magnesium hydroxide and aluminum hydroxide is used, whereas polyethylene, an ethylene/1-butene copolymer, an ethylene/propylene copolymer, an ethylene/vinyl acetate copolymer, an ethylene/ethyl acrylate copolymer, an ethylene/propylene/diene ternary copolymer or the like is used as the resin.
Meanwhile, very restrict flame retardance standards, for example, Vertical Flame Test defined in UL1581 (Reference Standard for Electrical Wires, Cables, and Flexible Cords)), etc., VW-1 standard, horizontal flame retardance standard as well as 60-degree inclined flame retardant characteristic defined in JIS C3005, and the like are required for insulated wires in light of safety.
Furthermore, such materials for covering electric wires may be required to show results meeting or exceeding a certain standard in a tensile elongation test, a tensile strength test, a heat deformation test and the like defined in JIS C3005.
However, when the resinous material such as polyethylene is used, it is difficult to meet or exceed a required standard in the heat deformation test.
Exemplary resins more likely to attain a favorable physical property in the heat deformation test include cyclic olefin-derived resins, and a resinous material for covering electric wire produced using a cyclic olefin-derived resin is illustrated in Japanese Unexamined Patent Application Publication No. H11-189743, the entire contents of which is hereby incorporated by reference in its entirety.
The resinous material for covering electric wire produced using a cyclic olefin-derived resin as described can meet or exceed a required standard in the thermal deformation test; however, meeting or exceeding a required standard is difficult in the tensile elongation test, in particular. Thus, a resinous material for covering electric wire having all required physical properties meeting or exceeding a certain standard has been demanded.